The Automatic Gearbox And Its Failings
Discussion
kapiteinlangzaam said:
Sump said:
use the throttle to control all the gear changes. It's very simple actually.
This! Learn the shift points of the box and drive accordingly.The problem these days is that most drivers seem to the think that the 3 (or 2) pedals are digital instruments, whereas I like to think they are analogue
jamieduff1981 said:
CrutyRammers said:
Never driven one that I liked at all. Now I've never driven a really modern one, but for the last 20 years people have been telling me "ah yes, old ones are bad, but the new ones...", and every time I try a new one they still seem to suck.
But each to his own. I just like changing gear anyway.
I like the tactility of changing gear manually when driving for pleasure. For commuting, it's a modern automatic every day for me.But each to his own. I just like changing gear anyway.
A car like the XFR(S) just wouldn't be any good with a manual gearbox, and passengers really wouldn't appreciate the whiplash from 500lb.ft disappearing and reappearing across a manual gear change. With the ZF 8 speed, it's virtually instantaneous. It changes softly when you're driving sensibly, and changes quickly when you're ragging it. It locks up in all gears properly - it's not floating around 2000rpm waiting for the car to catch up. It'll downchange properly when you tell it to complete with throttle blips and you can actually use engine braking to good effect unlike old-fashioned autos.
It seems that the great thing about the ZF in particular is that each car manufacturer can programme it any way they please to suit the character(s) of the car. I added the (s) there because the gearbox is very good at suiting the Jeckyll & Hyde alter-egos of performance saloons too that can be driven very smoothly or can be hooned around like a lunatic equally well.
Maybe they really are different this time - or maybe the flaws are just masked better with quicker reactions and more power.Like I say, each to his own. I can't imagine ever choosing an auto in any car myself.
I've just acquired a MK3 Mondeo with a slushbox fitted to it. Didn't want to buy it because its an auto and the reputation for the box is terrible. Driven autos in the past and liked them but not liked the repair cost. Then I stumbled upon this that had all the MK3 Mondeo issues sorted - the only thing that can go wrong is the box. Then weighed up the cost of a secondhand box and a DMF/Clutch etc replacement and thought sod it!
Actually nice not having to change down yourself etc - perfect for commuting and a motorway when you don't touch the box anyway. Just the fuel consumption bothers me! Actually very impressed with it - only shifts you notice are when its cold and its on fast idle etc and even then they arent a slam just more noticeable. Fluid levels bang on the money and nice and red.
Happy shedding!
Actually nice not having to change down yourself etc - perfect for commuting and a motorway when you don't touch the box anyway. Just the fuel consumption bothers me! Actually very impressed with it - only shifts you notice are when its cold and its on fast idle etc and even then they arent a slam just more noticeable. Fluid levels bang on the money and nice and red.
Happy shedding!
Likewise some variants of the dsg vw box - seat used a dsg in their nurburgring attack as it's notably quicker than the manual. The fuel consumption penalty came primarily from the torque converter so any auto without one will be as efficient (give or take) as the manual.
Manual will eventually become the 'base model' transmission as modern autos are so good, in jaguars and Mercedes it has been for many years.
Manual will eventually become the 'base model' transmission as modern autos are so good, in jaguars and Mercedes it has been for many years.
shambolic said:
7 speed auto in the SLK is cracking. And has flappy paddles if you really need them.
Merc's 7G-Tronic box is indeed a very competent auto. The original locked-up only in top whereas I believe the newer ones lock up in all gears. Very clever and work well with both the big capacity petrol engines as well as the torquey diesels.But you get the best out of them when you learn how to drive them. I rarely have to resort to manual control - only really when I want more engine braking and only then when I'm decelerating hard (heavy ML driven like a Caterham).
I've owned several autos and the main point of them is there is no clutch pedal.
That's what the government says anyway (from a licensing point of view).
So if the box changes itself that's a bonus. If it doesn't then I pull the selector.
I never used to mind pressing the gas pedal to get the right gear, but that suddenly seemed all wrong when we became all "green" and changing gear costs a bit of fuel....
That's what the government says anyway (from a licensing point of view).
So if the box changes itself that's a bonus. If it doesn't then I pull the selector.
I never used to mind pressing the gas pedal to get the right gear, but that suddenly seemed all wrong when we became all "green" and changing gear costs a bit of fuel....
The slush box in my 2.6 Omega needs to be controlled and driven. Stick it in D and just drive it wafts around and makes clumsy changes at inappropriate times.
If I use tactical use of the 'Sport' mode, it will hold the gear longer for sweeping bends or a series of corners. I even flick it into sport for bigger roundabouts so I don't get a mid junction change.
Often I'll use the stick to lock it into 2nd or 3rd on approaches to bends to get a smoother drive out, and then pop it back into D once I've cleared it.
It's all about how lazy you want to be and what you want the car to do.
If I use tactical use of the 'Sport' mode, it will hold the gear longer for sweeping bends or a series of corners. I even flick it into sport for bigger roundabouts so I don't get a mid junction change.
Often I'll use the stick to lock it into 2nd or 3rd on approaches to bends to get a smoother drive out, and then pop it back into D once I've cleared it.
It's all about how lazy you want to be and what you want the car to do.
Edited by wiliferus on Wednesday 16th July 21:56
Sheepshanks said:
I'm not sure what the problem is in that example - the autobox isn't psychic. Is this your 330i? I'd have thought that would get up to speed pretty rapidly without needing to boot it.
I do think autoboxes work well with turbo-diesels as they mask the limited rev range, and the diesel's torque will pick the car up from pretty well any speed in any gear once rolling - although I'd have thought a 330i would be good at that too. The only time I drive petrol autos any distance is in the US and they do seem more uncertain about what they're doing.
Yes, the 330i needs more than 5k rpm showing to produce meaningful acceleration. It can do the pottering about stuff reasonably well, but I only potter if I'm feeling exhausted. Between the two cars I currently own, I much prefer the 120 diesel with a manual 'box compared to the 3 litre straight 6 3-series with an auto.I do think autoboxes work well with turbo-diesels as they mask the limited rev range, and the diesel's torque will pick the car up from pretty well any speed in any gear once rolling - although I'd have thought a 330i would be good at that too. The only time I drive petrol autos any distance is in the US and they do seem more uncertain about what they're doing.
In my example, it's not really the auto's fault for changing up as it did, but more that it just isn't suited to that type of road at all and will therefore always select the wrong gear.
cerb4.5lee said:
TurboHatchback said:
There are good and bad boxes of course, bad ones are really obviously bad but good ones should be unnoticeable in their operation. I think that torque converter autos only work well with really torquey engines, either diesels or 4.0l+ petrols.
I think this hits the nail on the head and makes sense why the ZF slushbox doesn't work in my 330i very well and is a bad gearbox as the engine doesn't have much torque and it only has a relatively small capacity but as with anything you don't know until you try it and in our old 330d it seemed to worked a treat because of the torque and short powerband.I've been working on a gearbox conversion to fit a modern box into a classic car and have learnt quite a bit about how to install these types of boxes and get them to work properly. Obviously in OEM guise the TCU talks openly with the ECU and this allows torque management for smoother changes and the changing of line pressures based on engine criteria, rpm, throttle position and much more.
What I have noticed is that it takes hundreds of man hours to calibrate and tune the TCU for a specific application. It doesn't take many hours to get a lovely, smooth, predictable shift in normal driving conditions but it takes a massive amount of time to map each of the less common driving scenarios.
If we look at BMW, the ZF6 works wonderfully in their 3 series diesels, 5 and 7 series but the same unit is a bit of a turd in comparison in the 3.0 petrol small cars. If we then look at the classifieds I think we suddenly see the answer. BMW will sell nigh on 1m 3 series diesel autos, almost every 5 series will be an auto and diesel and all 7s are autos. In contrast they will only ever sell a few thousand 130 autos (none currently on PH and about 2 in AutoTrader) and still only ever sell a small number of 330 autos in relation to other models.
I think that because they know they will sell bugger all of these combos that they do not invest the hours in tuning the box to match the specific car. My guess is that they take the TCU map from a 5 Series petrol 6 or maybe even a 3 series diesel and just fine tune, re calibrate the basic everyday conditions in a few hours and leave the complex tuning as it wouldn't be profit efficient for the number of units they will sell.
However, a couple of the OPs issues are really down to driver misjudgement. The box can't predict the road ahead (apart from in a Rolls) it can only read the current data and make a descision. There are times when you know that these conditions are going to change quicker than the box can work out so you have to take control. Joining slip roads off roundabouts going uphill is a classic. You know exactly what is about to happen and what needs to be done but the gearbox has no data on how long the corner is, how steep the gradient is or that you now need to go from 30 to 70. It knows non of this and so you must take control by starting your exit from the apex by putting the car in the right gear yourself. So typically that means manually notching down a gear or two to find the bottom of the torque curve going into the start of the corner etc.
lord trumpton said:
we've recently bought an old gen X3 3.0d Auto.
Its the perfect family hack and the torquey diesel works well with the auto box. I couldn't have a TC auto box on a weekend car though - far too lethargic for a sporty type drive
This is a torque converter auto http://youtu.be/Ic3hmg4qb90 driven by PH round the Nurburgring for a recent article there's an ongoing thread about.Its the perfect family hack and the torquey diesel works well with the auto box. I couldn't have a TC auto box on a weekend car though - far too lethargic for a sporty type drive
I can't speak for anyone else but that gearbox is the furthest thing from lethargic and it's easily quicker than I could get through the T5 manual gearbox in my Cerbera. Despite being faster on paper, my Cerbera wouldn't see which way my wife's XF went, let alone the F-Type R. That's not the reason I'm keeping the Cerbera for the time being, but we all need to stop pretending manual cars are fast because nowadays because they just aren't. Certainly not when the clutch itself lasts under 30k when driving normally and costs £900 just for the parts. Powershifting and general mechanical abuse seem like a decidedly poor way to try to keep up with a modern auto in a powerful car. They can still be fun within the realms of our own little world when driving, but nobody is going to convince me they could hustle a comfortable, well equipped sports car round a challenging track like the Nurburgring quicker with a manual gearbox than they could with the ZF auto.
It's missing the tactility, I get that and somewhat subscribe to the idea myself, but the latest TC autos are anything but lethargic.
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